Question

我有两个表，一个名为os_files，包含上传文件的所有信息，还有os_files_downloads，每次下载文件时都会存储一条记录。

我想从os_files中删除自上载以来没有任何下载的记录，或上次下载时间为30天或更早的记录。到目前为止，我有以下代码，但它似乎没有用，有人能指出我正确的方向吗？另外我理解子查询很慢，有更快的方法吗？

SELECT `id`
FROM `os_files`
WHERE `uploadTime` < DATE_SUB(UNIX_TIMESTAMP(NOW()), INTERVAL 30 DAY)
  AND `id` NOT IN
    (SELECT `fileId`
     FROM `os_files_downloads`)
  OR `id` IN
    (SELECT `fileId`
     FROM `os_files_downloads`
     WHERE `timestamp` < DATE_SUB(UNIX_TIMESTAMP(NOW()), INTERVAL 30 DAY))

Answer 1

您只需要删除过去30天内未下载的所有ID。从逻辑上讲，这个集合还将包括从未下载过的任何ID：

SELECT `id`
FROM `os_files`
WHERE `id` NOT IN
    (SELECT `id`
     FROM `os_files_downloads`
     WHERE `timestamp` > DATE_SUB(UNIX_TIMESTAMP(NOW()), INTERVAL 30 DAY))

编辑：

假设os_files_downloads.id不是外键，那么你需要这个：

SELECT `id`
FROM `os_files`
WHERE `id` NOT IN
    (SELECT `os_files_id`   --or whatever the foreign key IS called
     FROM `os_files_downloads`
     WHERE `timestamp` > DATE_SUB(UNIX_TIMESTAMP(NOW()), INTERVAL 30 DAY))

Answer 2

此处一切正常您只需要通过中的外键替换'id'字段来自子查询 os_files_downloads ，可能 os_files_id ，并且 WHERE

后必须添加括号

示例：

SELECT id FROM os_files WHERE ( uploadTime < DATE_SUB(UNIX_TIMESTAMP(NOW()), INTERVAL 30 DAY) AND id NOT IN (SELECT os_files_id FROM os_files_downloads) ) OR id NOT IN (SELECT os_files_id FROM os_files_downloads WHERE timestamp > DATE_SUB(UNIX_TIMESTAMP(NOW()), INTERVAL 30 DAY))

错误地尝试通过 OR id NOT IN 更改 OR id IN ，并在最后一行 timestamp＆lt; DATE_SUB 按时间戳＆gt; DATE_SUB

请参阅上面给出的查询

Answer 3

好的伙计们，在摆弄身边后我终于做到了！答案如下，感谢您的帮助并推动我朝着正确的方向前进！

SELECT id 
FROM os_files 
WHERE uploadTime < UNIX_TIMESTAMP(NOW() - INTERVAL 30 DAY) 
AND id NOT IN (SELECT fileId 
               FROM os_files_downloads) 
OR id NOT IN (SELECT fileId 
              FROM os_files_downloads 
              WHERE timestamp > UNIX_TIMESTAMP(NOW() - INTERVAL 30 DAY))

选择多个条件和子查询

3 个答案: